Particle density porosimetry

Methods of measurement of coal density include use of a gas pycnometer and particle density by mercury porosimetry. However, the difference in density values using different gases must be recognized since, for example, density values measured by nitrogen may be greater than those obtained when helium is used. Density measurement depends on adsorption of gas molecules, and differences (between nitrogen and helium) may be due to nitrogen adsorption on the coal surface. 

A comparison of true particle density, apparent particle density, and bulk density can provide information on total porosity, interparticle porosity, and intraparticle porosity. Methods include true particle density measurements via helium pycnometry, mercury intrusion porosimetry, and poured and tapped bulk density. 

Although mercury porosimetry is principally concerned with the measure of the pore size, pore volume, and distribution, it also measures density—bulk density, particle density as well as skeletal density. Unlike other fluids, it does not spontaneously All pores but enters them only when a pressure is applied. The size of the pores that mercury enters is inversely proportional to the pressure (equilibrated) larger pores require less pressure compared to smaller pores. 

For porous particles with small pores, the particle volume in Eq. (15) should be replaced with the envelope volume of the particle as if the particles were nonporous as shown in Fig. 2. This would be more hydrodynamically correct if the particle behavior in the flow field is of interest or if the bulk volume of the particles is to be estimated. For total weight estimation, then the skeleton density should be known. The skeleton density is defined as the mass of the particle divided by the skeletal volume of the particle. In practice, the pore volume rather than the skeletal volume is measured through gas adsorption, gas or water displacement, and mercury porosimetry. These techniques will be discussed in more detail later. There are also porous particles with open and closed pores. The closed pores are not accessible to the gas, water or mercury and thus their volume cannot be measured. In this case, the calculated skeleton density would include the volume of closed pores as shown in Fig. 2. For nonporous particles, the particle density is exactly equal to the skeleton density. For porous particles, the skeleton density will be larger than the particle density. 

Very fine particles are fluidized forming agglomerates. Minimum fluidization velocity of such agglomerates Ma mf can be measured in the same manner as in the case of noncohesive particles, i.e., from the decreasing velocity period (period after 7 in Fig. 49). A partiele recycling device, such as a cyclone or a filter, is neees-sary for fine powder experiments. From Ma,mf apparent agglomerate size ean be determined from minimum fluidization veloeity eorrelations such as Wen and Yu s (1966) by using the particle density separately determined by mercury porosimetry or other methods. 

Porosimetry data can be graphed in a variety of ways and can be tailored to the purpose of the study. Plotting volume versus pore size will easily display the pore sizes observed in the sample. Pore size distributions can be calculated from the raw data and plotted to give the pore volume per unit radius interval. Other parameters can be calculated from porosimetry data, including average pore radius [40,48], surface area [7,39,40], pore surface area [6], particle size [40], and density [6,49]. 

Hg Porosimetry Fractional Volume of Carbon Densities Particle which is ... 

Mercury Porosimetry Method Mercury is a nonwetting liquid that must be forced to enter a pore by application of external pressure. Consequently it is an extremely useful and convenient liquid for measuring the density of powders and/or particles. This method can measure the apparent and true density of one sample by... 

In addition to surface fractal dimension ( Mercury Intrusion Porosimetry, under Boundary and Surface Fractal Dimensions ), this method can also be employed to determine mass fractal dimension of porous particles. Once the relative density of the particle at different pore volume, p, is obtained, then Dm can be deduced according to Eq. (20) ... 

The bulk densities were calculated from weight and volume measurements. Skeletal densities were measured by He pycnometry N2 adsorption-desorption isotherms were determined at 77 K on a Carlo Erba Sorptomatic 1900 and their analysis was done using a set of well-known techniques [5], Mercury porosimetry up to a pressure of 200 MPa is performed on a Carlo Erba Porosimeter 2000. Samples were examined using a transmission electron microscope to obtain particle and aggregate sizes [2]. 

The GMA-EGDM copolymer was synthesised from a GMA EGDM molar feed ratio of 31.5 68.5. The crosslinking density of the copolymer beads was 128%. Particle size of copolymer was in the range of 250-420 pm and the surface area estimated by single point BET method was 152 M / g. The pore volume estimated by mercury porosimetry was 0.74 cm /g. The polymer bound 2-picolyl amine was generated by the reaction of 2-picolyl amine... 

Mercury porosimetry provides a more quantitative method of characterizing the porosity in a particle compact. Bulk density, pore volume, mean pore size, and the pore size distribution of a powder compact can all be determined by mercury porosimetry. ... 

Gas adsorption measurements using the BET method offer an alternate, more precise method of determining 5, as well as the size and size distribution of meso-pores (8-1000 A) in a powder compact. Comparisons of the mean pore radius of high green-density CFG composites composed of micron-size particles determined by mercury porosimetry and from surface area measurements using Equation 5.5 show good agreement. 

Porosity and pore-size distributions were determined by gas adsorption and immersion calorimetry, with the measurement of helium and bulk densities. Volumes of micropores were calculated using the Dubinin-Radushkevich (DR) equation (Section 4.2.3) to interpret the adsorption isotherms of N2 (77 K), CO2 (273 K) and n-C4H o (273 K). Volumes of mesopores were evaluated by subtracting the total volume of micropores from the amount of nitrogen adsorbed at p/p° = 0.95. The two density values for each carbon were used to calculate the volume of the carbon skeleton and the total volume of pores (including the inter-particle space in monolithic disks). Immersion calorimetry of the carbon into liquids with different molecular dimensions (dichloromethane 0.33 run benzene 0.37 nm and 2,2-dimethylbutane 0.56 nm) permits the calculation of the surface area accessible to such liquids and subsequent micropore size distributions. The adsorption of methane has been carried out at 298 K in a VTI high-pressure volumetric adsorption system. Additional techniques such as mercury porosimetry and scanning electron microscopy (SEM) have also been used for the characterization of the carbons. 

By using Eq. (10) and the hole-particle symmetry of the lattice model we can transform the liquid porosimetry isotherm into an adsorption/desorption isotherm of density versus relative pressure for the wetting fluid. This is shown in Fig. 3 together with the gas adsorption results and the agreranent is excellent. 

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